CONCHIFERA. 435 
JRmpInA, Lamarck. 
Synonyms, Mutela, Scop. Spatha, Lea (including Mycetopus). 
Leila, Gray, 
Type, I. exotica, Pl. XVIII, Fig. 5. 
Etymology, iris, the rainbow. 
Shell oblong; umbones deprossed; hinge-line long, straight, 
attenuated towards the umbones, crenated by numerous unequal 
teeth ; ligament long and narrow. 
Animal with mantle-lobex united posteriorly, forming two 
short siphons; mouth and lips small; palpi immense, oval; gills 
united to the body. 
Iridina ovaia (Pleiodon, Conrad) has a broader hinge-line. 
Distribution, 9 species. Rivers of Africa, Nile, Senegal. 
Mycetorus, D’Orbigny. 
Etymology, mukes, a mushroom, pous, the foot. 
Type, M. soleniformis, Pl. XVIII., Fig. 6. 
“Shell elongated, sub-cylindrical, gaping in front; margins 
sub-parallel, hinge edentulous. 
Animal with an elongated, cylindrical foot, expanded into a 
disk at the end ; mantle open; gills equal; palpi short. 
Distribution, 3 species. River Parana, Corrientes; River 
Amazon, Bolivia. 
4HTHERIA, Lamarck. 
Type, Ai. semilunata, Pl. XVIII., Fig. 7. (Aitherios, aérial.) 
Shell irregular, inequivalve ; attached by the umbo, and 
tubular processes of one of the valves, usually the left ; epidermis 
thick, olive; interior pearly, blistered (as if with air-bubbles) ; 
hinge edentulous; ligament external, with a conspicuous area 
and groove in the fixed valve; two adductor impressions, the 
anterior very long and irregular; pallial line simple. 
Animal with the mantle-lobes open; body large, oblong, pro- 
jecting backwards; no trace of a foot; palpi large, semi-oval ; 
gilis sub-equal, plaited, united posteriorly, and to the body and 
mantle, 
Distribution, 4 species. River Nile, from first cataracts to 
Hazool;* River Senegal. 
MULLERIA, Férussac. 
Dedicated to Otto Frid. Miller, author of the ‘‘ Zoologia 
Danica.” 
Type, M. lobata, Fér., Fig. 222. 
Synonym, Acosteea (Guaduasana), D’Orbigny. 
* The “ fresh-water oysters ee by Bruce, 
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